Apparatus for making slide-fastener stringers

ABSTRACT

Slide-fastener stringers are made by extruding continuous strands of synthetic resin in a form having a plurality of cavities open on one side and defining the coupling head, shank and connecting portion of a multiplicity of coupling members which together form a coupling element adapted to be mounted along the edge of a support tape. An embossing tool is thrust into the connecting members and/or the shanks of the coupling members so as to plastically deform the thermoplastic material and produce humps along the surfaces of the coupling element which are thermally bonded to the support tape.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is related to my copending, commonly assigned,concurrently filed application Ser. No. 436,630, entitled SLIDEFASTENER.

FIELD OF THE INVENTION

The present invention relates to an apparatus for making a couplingelement for a slide fastener and for making a slide-fastener stringerhalf. More particularly, the invention relates to the production of animproved slide fastener with greater security of attachment of thecoupling element to a support tape.

BACKGROUND OF THE INVENTION

A slide-fastener stringer may comprise a pair of slide-fastener stringerhalves each of which can include a fabric support tape or band and acoupling element affixed to an edge of the support tape and adapted toengage or disengage with a complementary coupling element of the othersupport tape. The coupling elements may be more or less identical andcan have a plurality of coupling members relatively closely spaced apartalong the edge of the tape and generally projecting laterallytherebeyond.

Each coupling member may comprise a coupling head having formationsprojecting in the longitudinal direction, i.e. parallel to the edge ofthe tape along which they are disposed, fastening portions or shanksextending from each head transversely to this edge to overlie the tapeand provide a means whereby the coupling element or member may beaffixed to the tape and, in the case of continuous coupling elements, aconnecting portion or ligature joining the coupling members togetherinwardly of the tape edge.

The coupling heads of the two coupling elements interdigitate, i.e. fitbehind one another, so that the aforementioned formations engage toprevent or restrict lateral separation of the coupling elements in theabsence of movement of a slider along the two coupling elements. Theslider functions to bring the two coupling elements together or to slidethem apart in effecting the coupling or decoupling movement.

As pointed out in the aforementioned copending application, varioustechniques have been proposed heretofore for securing the couplingelements to the support tapes. These techniques may generally beconsidered to lie in three categories. In a first category is theattachment of the coupling element by loops of thread or by stitchingthe coupling element to the support tape with a row of chain or lockstitches, or by fitting the coupling heads through openings in the tapeor by weaving or knitting the coupling elements into the tape. A secondtechnique is the clamping of the individual coupling heads to edge ofthe tape by crimping or like technique. This latter method is used mostfrequently where the coupling element consists of a discontinuous chainof individual coupling members. In the third technique, continuouscoupling elements with a row of closely spaced heads are thermallywelded or adhasively bonded to the support tape or are anchored theretoby rivets, studs, or like widely-spaced pin-like formations insertedinto or formed on the extruded coupling element.

Several disadvantages have been encountered with the prior-art use ofthe last mentioned technique for securing coupling elements to a tape.Where the adhesive bonding or thermal welding approach has been usedheretofore, it has been the customary practice to bond the entiresurface of a coupling element confronting the tape to the latter. Thisgreatly limits the flexibility of the coupling element and prevents thetechnique from being used effectively for fine coupling elements, i.e.coupling elements with a very close spacing of the coupling heads.

When pins, studs or rivets have been used as described, they penetratethe fabric and are formed with heads on the side of the tape oppositethat from which they extend. The difficulty with this system is thatconsiderable localized stress is applied where each stud engages thefabric and these stresses can be sufficient to break the stud or tearthe fabric, thereby releasing the coupling element and rendering thestringer inoperative.

In the production of continuous coupling elements from thermoplasticsynthetic resins, it has been proposed heretofore by myself and mycoworkers on behalf of the present assignee, to pass the support tapethrough an extrusion head and to extrude a synthetic resin strand ontoand around the edge of the support tape, the strand being shaped by awheel provided with forming cavities or recesses along its periphery. Ithas also been proposed to continuously extrude a coupling element ofthermoplastic synthetic resin by passing an endless mold member providedwith a row of cavities through an extrusion head which fills thesecavities and then to strip the resulting shaped strands from the endlessmold thereby provided. In the first instance, the bond between thecoupling element and the tape is effected by imbedding the tape in thecoupling element strand with the disadvantage that shrinkage of thesystem occurs with a variation in the spacing and orientation of thecoupling heads which cannot be tolerated when the coupling elements areto be provided on garments. In addition, the penetration of thesynthetic resin varies from place to place along the textile tape andthus the quantity of synthetic resin available to fill each mold cavitymay vary so that some heads are incompletely formed. In general neitherof the aforementioned techniques, as practiced heretofore, is capable ofthe necessary provision to make fine slide fastener stringers at highrates and with good mechanical properties, i.e. high break or releaseresistance.

I have found, more specifically, that where the thermoplastic syntheticresin penetrates deeply into the body of the tape, the thermoplasticmass along the edge of the tape stiffens the latter while the tapefibers stiffen the thermoplastic mass so that a major part of theflexibility, desirable in a slide-fastener stringer, can be lost. Stiffslide-fastener stringers cannot be used in the garment industry.

Where attempts have been made to form the coupling element continuouslyand mount it upon the support tape by welding by thermal bondingtechniques, the aforementioned problem has not fully been eliminatedsince the substantially uniform bonding of all juxtaposed surfaces ofthe tape and the coupling elements also brings about stiffening to anundesired degree.

OBJECTS OF THE INVENTION

It is the principal object of the present invention to provide anapparatus for making a slide-fastener stringer half in which thecoupling element has uniform coupling heads of great precision oraccuracy and in which the problem of stiffening mentioned previously iseliminated.

It is another object of the invention to provide an apparatus for makinga slide-fastener stringer half of greater precision.

Yet another object of the invention is to provide an apparatus for theproduction of precision slide fasteners particularly suited for use inthe garment industry whereby the aforementioned disadvantages areavoided.

SUMMARY OF THE INVENTION

These objects and others which will become apparent hereinafter areattained, in accordance with the present invention, in a method of an anapparatus for the production of a slide-fastener stringer half in whichthe coupling element is formed from theremoplastic synthetic resin andis thermally bonded to a support tape, preferably but not necassarily atextile web, the coupling element being formed by extrusion ofthermoplastic synthetic resin material into a continuous and endlessform having a mulitplicity of cavities defining the coupling members andopen at one side of the form. According to this invention, a tool ispressed into the plastically deformable mass in each cavity to displacethe synthetic resin material around the tool and to cause it to swelloutwardly and form a mulitplicity of welding or fusion humps which aresubsequently fused to the support tape with the aid of which thecoupling element is withdrawn from the form.

Surprisingly, I have found that this technique achieves a dual purpose,namely, the provision of the aforementioned welding humps to which thebonding of the coupling element to the support tape can be confined sothat the stiffening problems hereto encountered do not arise. The secondphenomenon which results from the embossing operation effected by thetool is the displacement of the thermoplastic material into contact withall surfaces of the cavity so that each coupling member has aconfiguration and dimensions complementary to the use of the cavity inspite of the fact that some shrinking may have occurred in the course ofthe extrusion operation and partical cooling. In other words, when thesynthetic resin material is forced into the mold cavity, therefrequently is some shrinkage which causes portions of the thermoplasticmass to recede from the walls of the mold cavity at various locations sothat the coupling elements may be of irregular shape or may not be ofuniform dimensions. With the system of the present invention, wherebythe tool penetrates into the thermoplastic mass, there is a furtherextrusion of the material, outside the extrusion head so that thethermoplastic mass is forced into contact with all of the moldedsurfaces and, at the same time, sufficient synthetic resin material iscaused to well up adjacent the tool to form the welding humps. Thevolume of the tools impressed into the synthetic resin mass must thus besufficient to compensate for the shrinkage and the desired degree ofoutward welling of the synthetic resin material to form the hump.

According to an important feature of the invention, as was described inthe aforementioned copending application, each coupling member maycomprise a coupling head projecting beyond the edge of the support tapeand a fastenting portion or shank overlying the supporting tape. Inaddition, the connecting portions of adjacent coupling members may bejoined together unitarily by a connecting portion or ligature. Accordingto this invention, the tool is impressed into the mass of syntheticresin material representing the connecting portions or the fasteningportions or both. Since the head-forming part of the mold cavity alsocommunicates with the parts of the mold cavity defining the connectingand fastening portion, the lateral flow of synthetic resin materialcauses the latter to be pressed against all surfaces of the mold cavityand hence ensures uniform and precise shaping of the coupling head aswell.

It is therefore an important aspect of the invention that thethermoplastic synthetic resin in the mold cavity, while in a prehardenedor other plastically flowable state, is penetrated by a tool to displacethe plastic material outwardly under plastic-flow orpermanent-deformation conditions, whereupon some of the surfacesconfronting the tape are formed with welding humps and the support tapeis fused to the resulting coupling element and bonded thereto under heatand pressure. This type of thermal bonding can also be effected with theaid of ultrasonic welding devices in accordance with conventionalprinciples. The tape is thereupon drawn away from the endless moldelement to entrain the coupling element with it.

It should be noted that it is not necessary that the thermoplasticmaterial be embossed before it has completely hardened or cooled to atemperature below its plastic-flow temperature since the tool maypenetrate into the thermoplastic material with sufficient force and to asufficient degree to effect permanent displacement or plasticdeformation of even the fully hardened material. Furthermore, thepresent invention provides that the coupling heads may be constitutedwith formation, with the simultaneously embossing operation to ensureform-fitting engagement of the interdigitating coupling heads.

The bonding of the coupling element to the support tape is preferablyeffected, as indicated, with the aid of ultrasonic energy which iscontrolled so that the fusion occurs only in the region of the weldinghumps and it will be immediately apparent that the number and size ofthese humps can be determined by the volume of synthetic resin materialdisplaced to ensure a firm bond of the coupling element with the tapebut without stiffening of the system. Of course, where the problem ofstiffening is not as pronounced, i.e. in dependence upon the use towhich the slide fastener is to be put, it may be desirable to bond thecoupling element to the tape in other areas and over surfaces beyondthose afforded by the welding humps.

According to the invention, the coupling elements may be generally flat,i.e. have coupling members lying in a plane parallel to a surface of thetape to which the coupling element is bonded. In this case, the couplingelement lies only along one side of the tape. Alternatively, I mayprovide the coupling element so that it may be folded and each couplinghead defined as a bight between a pair of shanks which straddle the edgeof the tape. In this case, the pressure with which the two shanksembrace the tape increases the strength of the bond and each shank maybe provided along an inner space with the welding humps. The folding maybe effected after one shank has been bonded to the exposed surfaces ofthe coupling element in the endless mold to enable the tape to withdrawthe coupling element from the latter.

An important advantage of the system is that it allows a relativelysimple apparatus to be used to make the slide fastener stringer halfaccording to the invention. More particularly, the apparatus maycomprise a continuously moving endless mold element, e.g. a conveyorband, with an upwardly open mold cavity. Of, course, the endless moldmay also be a forming wheel if desired. The endless mold carrier maycooperate with compaction rollers for pressing the synthetic resinmaterial into the cavity and with shaving devices to trim excessmaterial projecting beyond the surface of the mold carrier at the sidethereof at which the cavities open.

According to the invention, the apparatus is provided with at least oneembossing wheel with a plurality of outward projections successivelypenetrating the masses of the synthetic resin materials in therespective mold cavities to displace these masses and form the weldhumps while forcing the synthetic resin material plastically into allportions of the mold. The system may be combined with means for feedingthe support tape into contact with the coupling element anmeans forthermoplastifying the humps to effect bonding between the support tapeand the coupling elements at these humps.

According to another feature of the invention, particularly where themold carrier is constituted as an endless band, the embossing wheelserves as an anvil for an ultrasonic tool for effecting thermal bondingsubstantially concurrently with the formation of the welding hump bydisplacement of the synthetic resin material, the sonotrode beingdisposed below the mold band. Furthermore, the embossing projection canhere penetrate the tape if desired.

Furthermore, the embossing wheel or roller can be provided ahead of themeans for feeding the support tape for the coupling element and thewelding device for fusing the tape to the coupling element. In this caseas well the welding device may be provided as an ultrasonic welding toolhaving a Sonar trode which acts upon the support tape via the latterupon the welding hump while the endless mold band or carrier constitutesthe anvil. When the mold carrier is in the form of a band, moreover, itmay move over another member consitituting the anvil. To maintain asubstantially uniform bond between the coupling element and the supportband, it has been found to be advantageous to provide downstream of thewelding means one or more elastic pressing rolls, the latter operatingupon the unit formed from the support tape and the coupling elementwhereby the coupling element can at this point remain in the endlessmold carrier or can have previously been lifted therefrom.

According to another feature of the invention, the mold carrier isprovided with recesses which produce the coupling members of a Uconfiguration, the U being formed by folding each coupling member aroundan edge of the tape. In this case the apparatus at an upstream locationprovides welding means to fuse the shanks of one side of each couplinghead to one surface of the tape while means is provided downstreamthereof to fold the coupling members successively around the edge andthen press the other shank of each coupling member against the tape viaa further welding device. The mold band or carrier may also extendthrough the second welding device and the bending or folding apparatusso as to maintain the desired spacing of the coupling members. In thiscase the portion of the coupling element previously fused to the supporttape may remain in the corresponding portions of the respective moldcavities.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will become more readily apparent from the followingdescription, reference being made to the accompanying drawing in which:

FIG. 1 is a perspective view, drawn to a larger-than-real scale of thedevice, illustrating an apparatus for carrying out the method of thepresent invention and wherein a reciprocal device represents theembossing wheel described previously;

FIG. 2 is a detail cross section taken along the line II--II of FIG. 1and drawn to a still larger scale;

FIG. 3 is a section taken generally along the line III--III of FIG. 1but of a scale corresponding to that of FIG. 2;

Fig. 4 is a schematic elevations view of another embodiment of theinvention;

FIG. 5 is a view similar to FIG. 4 illustrating a further embodiment;

FIG. 6 is a perspective view also in a relatively large scale, showinganother apparatus embodying the invention; and

FIG. 7 is a detail view diagrammatically illustrating the region VII ofFIG. 6.

SPECIFIC DESCRIPTION

FIG. 1 illustrates the principles of the present invention in somewhatdiagrammatic form. More specifically, in FIG 1 I show a coupling element1 which is formed by extrusion in an endless mold band or strip 3 of athermoplastic synthetic resin which is thermally bonded to a supporttape 2 along an edge thereof such that the coupling heads 5 of thecoupling element project laterally beyond the edge of the tape asrepresented in the upper right hand portion of this FIGURE.

The mold band or mold carrier 3, which is an endless strip displaced onrollers not shown by any conventional means through an extrusion headwhereby synthetic resin 9 is injected in a plastic flowable state intothe mold cavities 4, is shown after the resin has partly cooled andpossibly shrunk away from the edges of the cavity. The cavity has abottom 4a which is completely closed and is open along the upper surface4b. Each mold cavity comprsies a head-forming portion 4c, a shankforming portion 4d and a groove 4e which forms the connecting portion ofthe coupling element between the coupling members. Consequently, eachcoupling member comprises a head 5, as illustrated, in shank 5a aand aconnecting portion 5b joining the member with adjacent members to eachside thereof. The surfaces 5c and 5d of the shank 5a and the connectingportion 5b may be embossed as desceibed in the aforementioned copendingapplication and only diagrammatically illustrated in FIG. 1. Moreparticularly, an embossing tool 10 may be thrust into the surface toforce the synthetic resin material laterally into contact with all ofthe surfaces of each cavity and to cause material to well up in the formof an array of welding humps 11 along the edges of the recess 11a formedby the tool. In the system of FIG. 1, only the shank portions 5a areembossed so that the ligatures 8 between the coupling members remainunembossed although it will be apparent that the surfaces 5b may besimilarly embossed as described in the copending application mentionedpreviously.

While only a single element is shown to be formed on the band 3 of FIG.1 it will be apparent that it is just as convenient to form twocontinuous coupling elements with their heads directed in oppositedirections and to bond them simultaneously to two support tapes so that,one the slide fastener stringer half of each tape is withdrawn from theband 3 as illustrated at the right hand side of FIG. 1, the two slidefastener halves can be coupled together to form a stringer.

The tape 2 is fed to the coupling element 1 after the latter has beenprovided with the humps 11 by a tape-fed device represented generally at15 and including a guide roller 15a. The tape 2 passes between asonartrode 12 which is vertically movable as represented by the arrow Aand cooperates with an anvil 12 to thermally bond the coupling elementto the tape using conventional principles. Ultrasonic welding of thistype is fully disclosed in U.S. Pat. Nos. 3,330,026, 3,302,277,3,333,323, and 3,378,429. The untrasonic bonding joins the tape 2 to thecoupling elements at the connecting portion 7 of the shank (FIG. 3) andforms the slide fastener stringer half 7 which, upon deflection of thetape 2 around the roller 15b, draws the coupling element from the formband 3.

FIG. 2 shows how the embossing tool 10 can cause the synthetic resinmaterial to well up over the surface 4b of the band 3 and produce thehumps 11. Since the coupling elements are affixed to the support tapesubstantially only at these humps (FIG. 3) the stringer is uniformlyflexible and since the coupling heads 5 are always precisely complementsof the head portions 4c of their mold cavities, they are all ofidentical dimension and shape.

FIGS. 6 and 7 shown an embodiment of the invention in which the band 103carrying the mold cavities 104 passes over an anvil 112a juxtaposed withan ultrasonic head 112 for welding the tape 102 to the coupling element102. The difference between the device of FIGS. 6 and 7 and the deviceof FIGS. 1 through 3 derives from the conformation of the couplingelement.

In this latter embodiment, the coupling head 105 is originally formed asa flat enlargement having a plan symmetry through which a groove 105' isformed concurrently with the embossment of the recesses 111a in each ofa pair of shanks 106 extending at opposite directions from this head.Thus the upper surfaces of both shanks are provided with the humps 111baround the recesses 111a. The fastening portions or shanks 106 to eitherside of the head 105 are joined to the connecting portions or shanks ofadjoining heads between connection portions or ligatures 108 allunitarily formed as part of the coupling element 1. The thermoplasticmasses 109 within the correspondingly shaped recesses of the mold band103 are embossed by the vertically shiftable blade 110 which is pressedinto the thermoplastic material as described in connection with FIGS. 1through 3 and may represent an embossing wheel (see FIGS. 4 and 5).

The tape-feed device 115 of this embodiment comprises rollers asdescribed in connection with FIGS. 1 through 3 but only presses the tape102 on to the coupling elements along one side of the head, i.e. theleft-hand side as shown in FIG. 7. Consequently, only the left handfastening portion or shanks 106 are thermally fused to the tape when theunit passes between the sonatrode 112 of the anvil 112a. Thus, thecoupling element is bonded to the tape and can be drawn thereby awayfrom the form band 103 (see FIG. 6) whereupon the right hand side of thecoupling element is folded over (arrow B in FIG. 7) so that theconnecting portions or shanks now straddle the edge of the tape (seeupper portion of FIG. 6). The means for folding the tape also includesanother sonatrode 212 and an anvil 212a which together themally bond thehumps of both shanks of each coupling member to the tape. Of course, theband 104 can carry one side of the coupling element through theultrasonic unit if desired.

FIGS. 4 and 5 show that an apparatus for carrying out the process of thepresent invention can be relatively simple. Thus an endless form band303 can pass around the rollers 303a and 303b from an extrusion device,a blade 314 skimming excess synthetic resin from the surface of thisform at which the individual mold cavity opens. The form band may havethe configuration shown in either FIG. 1 or FIG. 6. A pressing roller313 cooperates with the roller 303a to urge the tape 302 against theform band carrying the coupling elements and the tape and couplingelements together are passed between an embossing wheel 316 having theembossing formation 310 (corresponding to the formations 10 and 110previously described), which produce the humps 11 (FIGS. 2 and 3) or111a, 111b (FIG. 7). In the embodiment of FIG. 4, however, the wheel 316also acts as an anvil for the Sonatrode 317 of the fusion device 312which simultaneously supplies the energy necessary to effect bonding ofthe humps as they are formed to the tape. A pair of pressing rollers 319downstream of the embossing and welding stage consolidate the unit andthe tape 302 is thereupon drawn away from the band 303 with the couplingelement 301 affixed thereto.

In the system of FIG. 5, the embossing wheel 416 carrying the embossingformations 410, produce the humps in the coupling element while it iscarried by the band 403 just behind the skimming blade 414. In thiscase, a single drum 418 serves to guide the band 403 from its forwardpass to its return pass and supports the band against the embossingwheel 316. The tape 402 is fed tangentially to the drum 408 which hereserves as the anvil for an ultrasonic traducer 417 carried by thewelding device 412, an elastically biased pressing roller 419 beingdeposited downstream of the welding station. The slide fastener half401, 402 being then drawn tangentially away from the band 403. In thesystem of FIG. 4, of course, the wheel 316 may constitute the Sonatrodeand member 317 the anvil.

I claim:
 1. An apparatus for making a slide-fastener stringer halfcomprising an endless mold carrier provided with successive cavities formolding a succession of thermoplastic synthetic resin coupling memberstogether forming a coupling element, the cavities being open to one sideand defining for each such member a coupling head, a fastening portionfor mounting the member on a tape, and a connecting portion for linkingeach member with an adjacent member; means for embossing the syntheticresin in each cavity at said fastening portion for displacing thesynthetic resin to form an array of welding humps at said fasteningportion while forcing the synthetic resin into contact with all of thesurfaces defining the respective cavity; and means for welding saidcoupling element to a support tape under heat and pressure at saidwelding humps, said embossing means including an embossing wheel havinga plurality of projections successively insertable into said cavitiesfrom said open side, said welding means including an ultrasonic tooljuxtaposed with said wheel, said wheel forming an anvil for saidultrasonic tool.
 2. The apparatus defined in claim 1 further comprisingelastic pressing rollers bearing against said coupling element and saidtape downstream of said welding means.
 3. An apparatus for making aslide-fastener stringer half comprising an endless mold carrier providedwith successive cavities for molding a succession of thermoplasticsynthetic resin coupling members together forming a coupling element,the cavities being open to one side and defining for each such member acoupling head, a fastening portion for mounting the member on a tape,and a connecting portion for linking each member with an adjacentmember; means for embossing the synthetic resin in each cavity at saidfastening portion for displacing the synthetic resin to form an array ofwelding humps at said fastening portion while forcing the syntheticresin into contact with all of the surfaces defining the respectivecavity; and means for welding said coupling element to a support tapeunder heat and pressure at said welding humps, said embossing meansincluding an embossing wheel having a plurality of projectionssuccessively insertable into said cavities from said open side, saidmold carrier being an endless band and said welding means including anultrasonic tool juxtaposed with said band, said band serving as an anvilfor said tool.
 4. The apparatus defined in claim 3, further comprisingelastic pressing rollers bearing against said coupling element and saidtape downstream of said welding means.
 5. An apparatus for making aslide-fastener stringer half comprising an endless mold carrier providedwith successive cavities for molding a succession of thermoplasticsynthetic resin coupling members together forming a coupling element,the cavities being open to one side and defining for each such member acoupling head, a fastening portion for mounting the member on a tape,and a connecting portion for linking each member with an adjacentmember; means for embossing the synthetic resin in each cavity at saidfastening portion for displacing the synthetic resin to form an array ofwelding humps at said fastening portion while forcing the syntheticresin into contact with all of the surfaces defining the respectivecavity; and means for welding said coupling element to a support tapeunder heat and pressure at said welding humps, said embossing meansincluding an embossing wheel having a plurality of projectionssuccessively insertable into said cavities from said open side, saidwelding means bonding said tape to one fastening portion of each memberand each member has two fastening portions extending in oppositedirections from said head, said apparatus further comprising means forfolding the other fastening portion of each member around an edge of thetape and further means for welding said other fastening portions to saidtape under heat and pressure, thereby forming said members with Uconfigurations straddling said tape.
 6. The apparatus defined in claim5, further comprising elastic pressing rollers bearing against saidcoupling element and said tape downstream of said welding means.